This invention relates to the preparation of iron phosphorus oxide catalysts useful for the oxidative dehydrogenation of organic compounds, such as for the preparation of unsaturated aldehydes and carboxylic acids from their corresponding saturated aldehydes and carboxylic acids.
More particularly, the present invention is directed to the preparation of highly active iron phosphorus mixed oxide catalysts in organic media, and the use of these catalysts for the oxydehydrogenation of aldehydes and acids, such as isobutyraldehyde to methacrolein and isobutyric acid to methacrylic acid.
Iron phosphorus oxide catalysts have been conventionally prepared by mixing and reacting compounds of the catalyst components in water, such as is disclosed in U.S. Pat. No. 3,948,959.
The dehydrogenation of aldehydes in the presence of at least two halogens and an inorganic catalyst which may comprise an alkali metal oxide or hydroxide or alkaline earth metal oxide or hydroxide and a metal compound such as iron phosphate, among others, is disclosed in U.S. Pat. No. 3,207,806.
The production of unsaturated carboxylic acids from their corresponding saturated acids using iron phosphorus oxide catalysts, with or without various promoters, is also disclosed in the art. U.S. Pat. No. 3,948,959 discloses the preparation of unsaturated acids by oxidation of the corresponding saturated acids using iron phosphorus oxide catalysts promoted with Li, Na, K, Rb, Cs, Mg, Ca, Sr and Ba. U.S. Pat. Nos. 3,634,494; 3,652,654; 3,855,279; 3,917,673 and 4,029,695 disclose the preparation of unsaturated acids and esters from saturated acids and esters using iron phosphorus oxide catalysts, containing bismuth and/or lead promoters, optionally with other promoter elements, including Mn, U, Pr, Ca, Sr, and Cr. These prior art catalysts characteristically have exhibited short life and thermal instability.
U.S. Pat. No. 4,244,879 discloses the preparation of vanadium phosphorus mixed oxide catalysts in organic media suitable for the reduction of vanadium from the +5 valence state to the +4 state.
It is therefore an object of the present invention to provide a process for the production of iron phosphorus mixed oxide catalysts, suitable for the oxydehydrogenation of saturated aldehydes and carboxylic acids, among other organic compounds, which exhibit high activity at moderate temperatures, extending catalyst life.